AQA 3.3.3 Digestion carbohydrates, lipids & proteins

Digestion: Hydrolysis of large molecules into smaller molecules, which are absorbed across teh cell membrane.

Carbohydrate digestion

  • take more than one enzyme to completely hydrolyse a large molecule.
  • the enzyme amylase is produced in the mouth and pancreas.
  • amylase hydrolases teh alternate glycosidic bonds of the starch molecule to produce teh diasaccharide maltose.
  • the maltose is in turn hydrolysed into alpha-glucose (monosaccharide) by maltase.
  • maltose is produced in the linging of the ileum

1) saliva enteres the mouth via salivary glands and is mixed with the food during chewing

  • saliva contains salivary amylase -> this starts hydrolysing any starch in the food to maltose. 
  • it conatins mineral salts that help maintain pH (around neutral), optimum pH for amylase to work.

2) food is swallowed and enters stomach (acidic pH), amylase is denatured due to acidic environment therefore starch cannot hydrolyse further. 

3) food passes into small intestine, mixes with pancreas secreation called pancreatic juice. It contains pancreatic amylase.

  • this continues the hydrolyisis of the remaining starch to maltose. (alkaine salts maintain a neutral pH for…


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